Hydrocarbons, and in particular petroleum, are produced from the ground as a mixture. This mixture is converted to useful products through separation and processing of the streams in reactors. The conversion of the hydrocarbon streams to useful products is often through a catalytic process in a reactor. The catalysts can be solid or liquid, and can comprise catalytic materials. In bi-functional catalysis, catalytic materials of acid such as zeolite and metals such as those in transition and main groups are combined to form a composite to facilitate the conversion process such as the one described in this subject application.
During the processing of the hydrocarbons, the catalysts deactivate over time. One primary cause of deactivation is the generation and buildup of non-volatile coke on the catalyst. The accumulation of non-volatile coke covers or blocks access to catalytic sites on the catalyst therefore, the spent catalyst is regenerated and returned to the reactor for further use. The regeneration of the catalyst is normally performed through the removal of the coke, where the coke is combusted at a high-temperature with a gas having oxygen. During the processing of the hydrocarbons, in addition to non-volatile coke lay down on the catalyst volatile hydrocarbons are also absorbed onto the catalyst. Prior to regeneration it is desirable to remove or strip the volatile hydrocarbons from the spent catalyst. Volatile hydrocarbons if not stripped properly will come off during high temperature regeneration or reactor conditions and faul the associated equipments such as reactor and regenerator internals, compressors, heat exchanging equipment, pipes and other vessels causing significant cleaning cost and reduction in plant operation time due to associated shutdowns. Preferred level of stripping necessitates high severity temperatures to desorb a substantial amount of volatilizable carbonaceous materials. Normally stripping is carried out in a so-called stripper, which is limited to low severeity temperatures enabling the catalyst to be lifted or transported to the regenerator. Low temperature operation invariably causes insufficient stripping of the volatile hydrocarbon species. Normally, this so-called stripper is an elongated vessel provided with side-to-side interior baffle. The spent catalyst is cascaded downwardly over the stripper baffle while the gas stream flowing counter currently to the descending catalyst.